1. Field of the Invention
The present invention relates to a text-to-speech synthesis apparatus, which inputs a text composed of a mixture of “HIRAGANA” and “KATAKANA” Chinese characters including a symbol such as a word, and composition, which then converts the input text into voice. More particularly, the present invention relates to processing symbols incorporated in a text.
2. Description of the Related Art
FIG. 8 is a constitution diagram of a conventional text-to-speech synthesis apparatus. Conventionally, the text-to-speech synthesis includes a text analysis unit 803 and a speech-synthesis-by-rule unit (parameter generator 805 and voice synthesis unit 806).
When a character column is input into a preprocessor 802, a character not to be read is deleted and an analysis unit (one sentence) is cut, and the sentence is output to a text analysis unit 803. In the text analysis unit 803, the sentence is decomposed into words by referring to a word dictionary 804; pronunciation, accent type of each word, and intonation of phrase are determined, and a phonetic symbol with a prosodic symbol (Interlanguage) is output. The speech-synthesis-by-rule unit includes a parameter generator 805 and a voice synthesis unit 806, and speech synthesis is performed based on the Interlanguage.
In the parameter generator 805, voice segment addresses in a voice segment dictionary 807 are selected, and pitch patterns, phoneme duration, pause length, amplitude, and the like are set.
In the voice synthesis unit 806, voice segment data corresponding to phonetic symbols are selected from voice segment dictionary 807, and voice segments are combined/changed to allow voice synthesis processing in accordance with a parameter determined in the parameter generator 805.
A text includes not only a general symbol including the end of a section of a word, a postpositional word and a phrase, a punctuation mark showing an end of a section, and a colon/or semi colon showing apposition/exemplary but also various symbols such as an interval, a bracket, a scientific symbol, a unit symbol, a rule and a special symbol. When all kinds of symbols in input text are spoken, it is useful for the particular application such as collation check to be carried out. However, when these symbols are spoken, the sounds of the symbols irritate users in general use.
However, a conventional synthesis apparatus provides an operation mode to read a symbol, and also provides an operation mode not to read aloud the symbol, so that the user may be capable of selecting the mode. In a normal operation the mode is set not to read aloud a symbol character. In a preprocessor 802 of FIG. 8, a symbol character in a text is detected. The symbol is deleted and then the text is analyzed when the operation is set so as to not read the symbol.
On the other hand, there is a case where reading of the symbol is not limited and the symbol character should be spoken as the symbol. In that case, the continuous symbol is used as a paragraph section line as an expression often used in a general text such as “-----”. If a symbol column in this case is output by voice such as hyphen, hyphen, hyphen, . . .  per one character, this further irritates users.
A module to judge a plurality of successive symbols in a preprocessor and a countermeasure is taken as disclosed in, for example, Japanese Laid Open publication No. 9-016196. The countermeasure is that for N or more number of symbols, even if read, the symbol is set and is output as another reading, a sign tone, a voiceless part, a different speed, sound quality, and a synthesis tone of sound volume, which are listened to without any feeling.
In recent years, voice quality of a text-to-speech synthesis apparatus has rapidly improved, and voice guidance in car navigation and voice auto information guide systems have become more common. The ability to read aloud electric mail is one of the main applications. Electronic mail has expressions such as a visual variety of intensions or appearances arising from recent rapid use.
A simple description such as a line of asterisks (*) or hyphens (-) is not used for a paragraph section line but various descriptions are used as shown in a table 1. Descriptions shown in table 1 are just one example, however, in all examples, detection is not possible in a conventional manner to judge symbol repetition. There is a problem that the conventional systems read aloud all symbols in one line, or one part of a symbol in a line as the symbol is spoken.
TABLE 1No.Expression's example of paragraph section line1 2 3 4 5 6 7 8 9 10 11 